Blood sampling apparatus containing an anticoagulant composition

ABSTRACT

Disclosed is a blood sampling apparatus containing an anticoagulant composition which allows for the accurate analysis of blood electrolyte concentrations. The claimed apparatus comprises a receptacle, a blood inlet and the disclosed anticoagulant composition which does not unduly bind sodium, potassium or calcium ions from the sampled blood.

This is a divisional of U.S. Ser. No. 08/096,123, filed on Jul. 22,1993, now U.S. Pat. No. 5,336,620, which is a continuation of U.S. Ser.No. 08/009,627, filed on Jan. 27, 1993, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a process for the production of ananticoagulant composition, as well as the composition so produced. Thepresent invention further relates to an apparatus containing suchcomposition for use in the sampling of blood and a method of samplingblood.

BACKGROUND OF THE INVENTION

The analysis of whole blood requires the use of an anticoagulant,typically in the collection apparatus, in order to prevent coagulationof the collected blood sample prior to its analysis. The use of heparin,both in dry and liquid form, is known, as is its ability to bind acertain portion of the electrolyte within the blood sample (e.g. sodium,potassium and/or calcium ions). This electrolyte binding is undesirablesince it effectively prohibits an accurate analysis of blood electrolyteconcentration, particularly sodium, potassium and calcium ionconcentrations. The measurement of calcium ion concentration hasrecently received increased attention in the field of cardiac medicinein view of the heart's sensitivity to calcium ion concentration and therecent development of blood gas machines to monitor the concentrationthereof.

Various solutions to the problems associated with this electrolytebinding by heparin have been heretofore proposed. For instance,Radiometer SA of Copenhagen has previously marketed anticoagulantcompositions for use in connection with blood sampling apparatus in theform of capillary tubes having a coating on the inner wall of the tubeof dry sodium heparinate. These compositions are further said to containa specified amount of calcium chloride in an effort to compensate forthe blood's calcium anions which will be bound by the heparinate once insolution. The use of this composition therefore does not provide acomplete solution to the aforementioned problem since this compositionintroduces additional sodium and chloride ions into the blood sample,thereby altering an accurate analysis of the concentration of sodium andchloride within the blood sample. Moreover, the added calcium ionsrepresent only a replacement for an approximation of those expected tobe bound by the heparin component. Therefore, an analysis for calciumion concentration within the collected sample while improved, is notrendered totally accurate.

U.S. Pat. No. 4,687,000 (assigned to Radiometer A/S) discloses a methodfor treating a blood sample with an anticoagulant as well as a bloodsampling device. The disclosed method involves contacting a collectedblood sample with (a) an anticoagulant capable of binding cation specieswithin the blood and (b) an additive including selected cationic speciesin the amounts compensating for proportions of these cation speciesbound by the anticoagulant. The disclosed method still does notrepresent a true solution to the aforementioned problems, however, sinceagain the cationic species present in the additive represent onlyestimations of the cations expected to be bound rather than the true andexact amounts.

It is therefore an object of the present invention to provide a processfor the production of an anticoagulant composition.

It is further an object of the present invention to provide a method fortreating blood with anticoagulant which allows for accurate analysis ofthe sodium, potassium and calcium ions present therein.

It is further an object of the present invention to provide an apparatuswhich is both a container for the claimed anticoagulant and useful inthe practice of the claimed method.

SUMMARY OF THE INVENTION

The present invention comprises a process for the production of ananticoagulant and the anticoagulant produced thereby.

The present invention further is directed to a blood sampling devicecomprising

(a) a receptacle means defining a blood receiving space therein forreceiving a blood sample;

(b) a blood inlet means for introducing a blood sample into the bloodreceiving space; and

(c) an anticoagulant present within said blood receiving space, saidanticoagulant comprising the product of the process of claim 1.

The present invention further comprises a method for collecting bloodsamples through use of the claimed composition.

DESCRIPTION OF THE FIGURE

FIG. 1 is a cross-section of a syringe useful in the practice of thepresent invention as a blood collection device. The syringe provides areceptacle means defining a blood receiving space and a blood inletmeans for introducing a blood sample into the blood receiving space.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

As stated above, the present invention relates to a novel anticoagulantcomposition and the process for its production. The invention furtherrelates to an improved method for the collection of blood samples and anapparatus useful in the practice thereof.

The anticoagulant composition of the present invention is lithiumheparinate modified with a heavy metal salt such as zinc acetate. It isproduced through a procedure which is outlined below.

A quantity of sodium heparin is obtained and dissolved in water to aconsistency such that it is suitable for passage through a bed of an ionexchange resin. Sodium heparin is obtained from various sources such asbeef lungs and/or mucosa, pork mucosa, and whole pork intestines. It isfurther commercially available from such sources as Viobin Corporationof Waunakee, Wisconsin. Preferably, the solution so formed has aconcentration of about 30,000 to about 50,000 u/cc.

The solution is then passed through a column of an acidic ion exchangeresin. The resin may comprise any acidic ion exchange resin or mixturesthereof. Such resins include IR-120 (a resin available from Rohm andHaas Company having a matrix structure of divinylbenzene (8%) and asulfonic acid functionality). Preferred is the IR-120 resin. Especiallypreferred is the use of IR-120 resin in the hydrogen form. The effluentfrom the ion exchange column is collected and monitored for the presenceof heparin such as through the use of toluidine blue. The effluentshould further possess a pH of 3 or less. The acidity of the effluentcan be maintained through adjustment of the residence time of thesolution within the ion exchange column.

The acidic heparin effluent is then converted to a heavy metal heparinsalt through contact with a heavy metal-containing compound. Conversionto a zinc, barium or copper salt is preferred. These salts include zincacetate dihydrate as well as the chlorides and sulfates of zinc, bariumand copper. Use of zinc acetate dihydrate is preferred. In the casewhere zinc acetate dihydrate is used, it is added to the acidic effluentin an amount ranging from about 2 to about 7 grams, preferably about 5grams, per each 15 grams of sodium heparin originally introduced intothe ion exchange column. Use of other of the above-named heavy metalcontaining compounds include the use of similar molar amounts. The pHsolubility of the solution is further monitored to ensure that the pH ismaintained so as not to exceed about 3.

To the heparin-heavy metal salt produced in the preceding step is thenadded an aqueous solution of lithium salts such as lithium acetate,lithium hydroxide or lithium carbonate such that the resulting solutionpossesses a pH in the range of about 6 to about 7. The use of lithiumhydroxide is preferred. Use of an aqueous 10% lithium hydroxide solutionis especially preferred. This solution is agitated, typically for aperiod of about 4 to about 24 hours, preferably at least 8 hours, topermit for chelation of the lithium and stabilization of the solution'spH. Additional amounts of either solution may of course be added tocorrect for pH deviations.

The pH stabilized solution may then be filtered through a filter mediasuitable to remove any bacterial contamination and/or insoluble matterpicked up during prior processing. Use of a media having a pore size ofabout 0.22 microns is preferred. The filtered solution may then be driedin a suitable apparatus such as a Lyophilizer produced by Hull orVirtis.

Drying times and temperatures should be maintained at a level such thatundue degradation of the heparinate composition is avoided. Once dried,the heparin composition should further be preferably stored in an areaof low humidity in view of the hydroscopic nature of the material.

The claimed composition is found to possess about 6 to about 8% byweight of zinc through atomic absorption spectroscopy. If heavy metalsother than zinc were used, the claimed composition contains equivalentmolar amounts of such metals.

The amount of the heparin composition used in conjunction with sampledblood should be sufficient to ensure against coagulation of the bloodsample. However, use of great excesses of the composition should also beavoided in order to minimize any potential interference in the analysisof the collected blood sample. It is therefore preferred that use bemade of the least amount of the anticoagulant composition whichadequately prevents blood sample coagulation. It has been found, forexample, that the use of about 8 to about 150 international units (IU)of the composition per milliliter of sampled blood is useful in thepractice of the claimed method. Preferably, about 20 to about 80 IU/mlare used. Most preferably, about 50 IU/ml are used. The above quotedranges for the concentration of anticoagulant adequate to prevent bloodcoagulation are concentrations which are recognized as useful incollection devices and indeed are present in products which arecurrently commercially available. These ranges do not however refer touse in Sherwood ABG syringes described herein.

However, it should be noted that lower concentrations of anticoagulantare being increasing used and recommended. For instance, the proposedguidelines issued in September 1992 by the NCCLS subcommittee onElectrolytes (Document C31-P) recommends the use of heparinate in anamount of about 15 IU/ml. Lower concentrations (e.g. below 10 IU/ml)have also been reported as sufficient. Indeed Sherwood Medical ABGsyringes currently contains 12 (+/-2) IU/ml of heparinate. Use of suchlower levels of anticoagulant is within the scope of the presentinvention.

The claimed anticoagulant composition may be predissolved prior to itsbeing contacted with a collected blood sample or, more preferably,utilized in its dried state wherein it is dissolved upon its contactwith the collected blood sample. Most preferably, the composition ispresent in dried form within the collection apparatus for the bloodsample, i.e. capillary tube, syringe or vacuum container. In this way,it is available for immediate contact with the sampled blood as it iscollected. The dried form of the claimed composition may be presentwithin the collection apparatus as a free solid (i.e. powder) or as afilm or coating present on the walls or other internal structure of thecollection apparatus. For instance, the composition may be deposited onor within an inert carrier body, such as disclosed in U.S. Pat. No.4,687,000, the contents of which are hereby incorporated by reference.

The invention disclosed herein is further described through thefollowing illustrative examples. Such examples are not intended, norshould they be construed, as limitations to the scope of the presentinvention.

EXAMPLE I

Approximately one kilo of sodium heparin (manufactured by the ViobinCorporation) is dissolved to form an aqueous solution having aconcentration of 30,000 to 50,000 u/cc.

A column of about 9 liters of IR-120 Plus ion exchange resin in thehydrogen form is prepared and then washed with a sufficient quantity ofwater. The heparin solution is then introduced into the column and thepH of the effluent is monitored with Toluidine Blue. The pH of theeffluent is maintained at 3 or less. The effluent is collected.

Zinc acetate dihydrate is added to the collected effluent in an amountof about 3 to about 7 grams of the zinc salt per each 15 grams of thestarting amount of sodium heparin. A sufficient amount of a 10% aqueoussolution of lithium hydroxide is added such that the resulting solutionhas a pH of about 6.0 to about 6.5. The solution is then allowed tosettle overnight. In the morning, the solution is filtered through a0.22 micron filter media. The solution is dried through the use of aHull Lypohizer and the resulting product is stored in a low humidityarea.

EXAMPLE 2

A stock solution of the heparin composition produced in Example 1 isprepared by dissolving about 1,440,000 USP units in about 1,000 ml ofdeionized water. The resulting solution possesses about 1,440 USPunits/mi.

By means of a pipette, 0.025 ml of the heparin solution is placed in asyringe (ABG brand manufactured by Sherwood Medical) in the 45° creasein the barrel. The solution is then dried by means of the lyophilizationmethod. The dried heparinate cakes in the syringe contain about 36±6 USPunits of heparinate. The final heparin concentration in blood samplescollected in these syringes should therefore be in the range of 12±2 USPunits/mi.

The syringes are then used in the collection of blood. The syringes arefilled completely and/or partially with blood and the specimens are thenanalyzed for electrolytes. Similar quantities of blood are alsocollected in heparin-containing syringes manufactured by Radiometer(type Smooth-E Arterial Blood Sampler) and Sherwood Medical (Type ABG)as well as a syringe having no heparinate contained therein (control).

The test results and a summary of a statistical analysis of said resultsare presented in Tables 1, 2 and 3.

                                      TABLE I                                     __________________________________________________________________________    Comparison of Ionized Calcium Values Obtained from Blood Specimens            Collected in                                                                  Plain Syringes (Control) Versus Heparinized Syringe Types                     with Varied Draw Volumes.                                                     Draw Volume  X (±SD).sup.a                                                                     Comparison to Plain Syringe                               Syringe                                                                            ml      mg/dL  Slope                                                                             Intercept                                                                          Correl Coef                                                                          p =                                       __________________________________________________________________________    Control      4.87 (±0.12)                                                  A    3.0     4.91 (±0.11)                                                                      1.02                                                                              -0.12                                                                              0.95   0.02                                           1.0     4.93 (±0.11)                                                                      1.02                                                                              -0.17                                                                              0.96   <0.01                                          0.75    4.91 (±0.10)                                                                      1.19                                                                              -0.99                                                                              0.94   0.02                                      B    3.0     4.79 (±0.11)                                                                      1.06                                                                              -0.21                                                                              0.94   <0.01                                          1.0     4.59 (±0.12)                                                                      0.98                                                                              0.39 0.93   <0.01                                          0.75    4.48 (±0.14)                                                                      0.83                                                                              1.14 0.93   <0.01                                     C    3.0     4.83 (±0.11)                                                                      0.87                                                                              0.68 0.82   0.08                                           1.0     4.85 (±0.11)                                                                      1.02                                                                              -0.09                                                                              0.92   0.21                                           0.75    4.86 (±0.10)                                                                      1.05                                                                              -0.22                                                                              0.89   0.66                                      __________________________________________________________________________     .sup.a n is 10 for all syringe types                                     

A represents a 6 ml (3 ml draw) syringe manufactured by Sherwood MedicalCompany which contains the lithium heparinate modified with zinc acetateproduced in accordance with Example 1 and claimed herein.

B represents a 6 ml (3ml draw) syringe which contains lithium heparinproduced by Viobin Corporation.

C represents a 3 ml syringe (3 ml draw) produced by Radiometer A/S andmarketed under the tradename Smooth-E Arterial Syringe. It contains alithium heparin anticoagulant and additional anions as describedpreviously herein.

The above data shows that samples collected with Syringe A exhibitedgood correlation coefficients relating to ionized calcium at all bloodvolumes and acceptable slopes an intercepts. Heparin interference withquantifiying ionized calcium concentration even when the proportion ofheparin was effectively increased by partially filling the syringe withsampled blood was therefore reduced. Similar results were exhibited withSyringe C. As expected, syringes containing plain lithium heparin(Syringe B) exhibited significantly lower ionized calcium valuesrelative to the control data, presumably due to binding of calcium ionswith the heparin.

EXAMPLE 3

The procedure of Example 2 was repeated except that the samples werethen tested for potassium concentration rather than ionized calciumconcentration. The results of Example 3 are presented in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    COMPARISION OF PLASMA POTASSIUM VALUES OBTAINED                               WITH VARIED DRAW VOLUMES                                                      DRAW                Comparison to Control Syringes                            VOLUME     N =                                                                              X (±SD)         CORREL                                       SYRINGES   (ml)                                                                             (mmol/L)                                                                            SLOPE                                                                              INTERCEPT                                                                             COEF. P =                                    __________________________________________________________________________    Control    9  4.2 ± 0.2                                                    A    3.0   9  4.1 ± 0.2                                                                        0.64 1.5     0.75  0.50                                        0.75  8  4.1 ± 0                                                                          0.74 1.1     0.79  0.33                                   B    3.0   9  4.1 ± 0.2                                                                        0.76 1.0     0.77  0.5                                         0.75  9  4.2 ± 0.2                                                                        0.52 2.0     0.50  0.88                                   C    3.0   0  4.2 ± 0.1                                                                        0.55 1.9     0.78  0.35                                        0.75  9  4.4 ± 0.3                                                                        0.77 1.1     0.64  0.02                                   __________________________________________________________________________

It can be seen through the mean value data set forth in Table 2 thatSyringe A and B exhibited satisfactory results relative to the controlsyringe on both full draw and short draw samples. In contrast, samplescollected with Syringe C exhibited a significantly higher potassium ionconcentration at reduced blood draw volumes.

EXAMPLE 4

The procedure of Example 2 was repeated except that the samples weretested for total calcium concentration rather than ionized calciumconcentration. The results of Example 4 are presented in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    COMPARISION OF TOTAL CALCIUM CONCENTRATION                                    OBTAINED WITH VARIED DRAW VOLUMES                                             Draw Volume  X (±SD).sup.a                                                                     Comparison to Plain Syringe                               Syringe                                                                            mL      mg/dL  Slope                                                                             Intercept                                                                          Correl Coef                                                                          p =                                       __________________________________________________________________________    A    3.0     9.4 (±0.2)                                                                        0.80                                                                              1.9  0.83   0.15                                           1.0     9.3 (±0.2)                                                                        0.79                                                                              2.2  0.81   <0.01                                          0.75    9.3 (±0.3).sup.b                                                                  0.60                                                                              4.1  0.63   0.04                                      B    3.0     9.4 (±0.2)                                                                        0.96                                                                              0.4  0.90   0.04                                           1.0     9.3 (±0.2)                                                                        0.84                                                                              1.7  0.82   <0.01                                          0.75    9.3 (±0.3).sup.c                                                                  0.19                                                                              7.6  0.36   0.31                                      C    3.0     9.9 (±0.3)                                                                        0.67                                                                              2.0  0.70   <0.01                                          1.0     11.0 (±0.3)                                                                       0.53                                                                              3.6  0.56   <0.01                                          0.75.sup.b                                                                            11.4 (±0.4)                                                                       0.38                                                                              5.1  0.67   <0.01                                     Control      9.5 (±0.2)                                                    __________________________________________________________________________     .sup.a n = 10 for all syringe types.                                          .sup.b n = 4                                                                  .sup.c n = 7                                                             

It can be seen through the data set forth in Table 3 that the meanvalues of Syringe A and B were within 0.2 mg/dL relative to the plainsyringe, even at reduced draw volumes. In contrast, the use of Syringe Cyielded results which were modestly higher at full draw volumes andsignificantly higher at partial draw volumes. This demonstrates theartificial increase in total calcium values associated with the use ofsyringes such as Syringe C in partial draw blood sampling.

EXAMPLE 5

The procedure of Example 1 was followed such that four (4) separatebatches of the heparin composition claimed herein were prepared. Eachbatch differed only in the amount of zinc acetate utilized. The batchesused 3.0, 3.2, 4.0 and 5.0 grams of zinc acetate per 15 grams of initialsodium heparin.

The resulting heparin compositions were then placed within 6 ml (3 mlfull draw) syringes per the procedure set forth in Example 2. Wholeblood samples were then drawn in the various quantities noted in Tables4, 5 and 6. Said samples were then analyzed for both ionized calciumconcentrations and pH. The results of said analyis are also set forth inTables 4, 5 and 6.

                                      TABLE 4                                     __________________________________________________________________________              WHOLE BLOOD                                                                   TOTAL VOLUME        IONIZED CALCIUM                                 HEP. SALT PER SYRINGE                                                                             TOTAL HEPARIN                                                                           mg/dl       pH                                  MODIFICATION                                                                            (ml)      units/syringe                                                                           DONOR A                                                                             DONOR B                                                                             DONOR A                                                                             DONOR B                       __________________________________________________________________________    3.0 grms  3.0       36        5.08                                                                             5.04                                                                             5.04                                                                             5.08                                                                             7.39                                                                             7.39                                                                             7.37                                                                             7.37                       ZnAc      1.5       72        5.04                                                                             5.00                                                                             5.00                                                                             5.04                                                                             7.39                                                                             7.39                                                                             7.37                                                                             7.36                                 0.75      144       4.92                                                                             4.96                                                                             4.88                                                                             4.92                                                                             7.39                                                                             7.38                                                                             7.36                                                                             7.36                                 0.43      251       4.72                                                                             4.68                                                                             4.68                                                                             -- 7.38                                                                             7.37                                                                             7.36                                                                             --                                   0.30      360       4.56                                                                             4.60                                                                             4.48                                                                             4.40                                                                             7.36                                                                             7.37                                                                             7.38                                                                             7.38                       3.2 gms   3.0       36        5.04                                                                             5.00                                                                             5.04                                                                             5.04                                                                             7.39                                                                             7.39                                                                             7.37                                                                             7.36                       ZnAc      1.5       72        5.08                                                                             5.04                                                                             5.04                                                                             5.04                                                                             7.39                                                                             7.39                                                                             7.37                                                                             7.36                                 0.75      144       4.96                                                                             4.96                                                                             4.92                                                                             4.92                                                                             7.39                                                                             7.39                                                                             7.37                                                                             7.36                                 0.43      251       4.80                                                                             4.80                                                                             4.72                                                                             4.76                                                                             7.37                                                                             7.37                                                                             7.36                                                                             7.35                                 0.30      360       4.68                                                                             4.68                                                                             4.44                                                                             4.52                                                                             7.37                                                                             7.36                                                                             7.35                                                                             7.36                       CONTROL (A)                                                                             1.0       none      5.12        7.38                                CONTROL (B)                                                                             1.0       none      5.12        7.38                                __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________              WHOLE BLOOD                                                                   TOTAL VOLUME        IONIZED CALCIUM                                 HEP. SALT PER SYRINGE                                                                             TOTAL HEPARIN                                                                           mg/dl       pH                                  MODIFICATION                                                                            (ml)      units/syringe                                                                           DONOR C                                                                             DONOR D                                                                             DONOR C                                                                             DONOR D                       __________________________________________________________________________    4.0 grms  3.0       36        4.88                                                                             4.92                                                                             5.00                                                                             5.12                                                                             7.40                                                                             7.40                                                                             7.41                                                                             7.40                       ZnAc      1.5       72        4.92                                                                             4.96                                                                             5.08                                                                             5.16                                                                             7.40                                                                             7.39                                                                             7.40                                                                             7.40                                 0.75      144       -- 4.92                                                                             5.04                                                                             5.12                                                                             -- 7.39                                                                             7.40                                                                             7.40                                 0.43      251       4.56                                                                             4.64                                                                             4.88                                                                             4.96                                                                             7.38                                                                             7.37                                                                             7.40                                                                             7.39                                 0.30      360       4.48                                                                             4.44                                                                             4.68                                                                             4.76                                                                             7.36                                                                             7.36                                                                             7.39                                                                             7.39                       CONTROL (C)                                                                             1.0       none      5.04                                                                             --       7.39                                                                             --                               CONTROL (D)                                                                             1.0       none         5.12        7.40                             __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________              WHOLE BLOOD                                                                   TOTAL VOLUME        IONIZED CALCIUM                                 HEP. SALT PER SYRINGE                                                                             TOTAL HEPARIN                                                                           mg/dl.sup.2 pH                                  MODIFICATION                                                                            (ml)      UNITS ML  DONOR A                                                                             DONOR B                                                                             DONOR A                                                                             DONOR B                       __________________________________________________________________________    5.0 grms  3.0       30        5.04                                                                             5.00                                                                             5.04                                                                             4.96                                                                             7.39                                                                             7.39                                                                             7.44                                                                             7.44                                           42        5.00                                                                             4.96                                                                             5.00                                                                             5.00                                                                             7.43                                                                             7.43                                                                             7.44                                                                             7.44                                 1.5       60        5.04                                                                             5.00                                                                             5.04                                                                             4.96                                                                             7.41                                                                             7.41                                                                             7.44                                                                             7.44                                           84        5.00                                                                             5.08                                                                             5.00                                                                             5.00                                                                             7.43                                                                             7.43                                                                             7.44                                                                             7.44                                 0.75      120       5.00                                                                             5.00                                                                             5.00                                                                             4.96                                                                             7.42                                                                             7.42                                                                             7.44                                                                             7.44                                           168       4.96                                                                             5.00                                                                             4.96                                                                             4.96                                                                             7.41                                                                             7.41                                                                             7.43                                                                             7.43                                 0.43      209       4.88                                                                             4.88                                                                             4.83                                                                             4.84                                                                             7.42                                                                             7.42                                                                             7.44                                                                             7.43                                           293       4.72                                                                             4.68                                                                             4.76                                                                             4.72                                                                             7.39                                                                             7.40                                                                             7.42                                                                             7.42                                 0.30      300       4.76                                                                             4.76                                                                             4.68                                                                             4.68                                                                             7.41                                                                             7.40                                                                             7.42                                                                             7.43                                           420       4.48                                                                             4.48                                                                             4.36                                                                             4.44                                                                             7.37                                                                             7.38                                                                             7.40                                                                             7.40                       CONTROL (C)                                                                             1.0       none      5.04                                                                             5.08                                                                             5.00                                                                             5.00                                                                             7.40                                                                             7.40                                                                             7.44                                                                             7.44                       CONTROL (D)                                                                             1.0       none      5.00                                                                             -- 4.96                                                                             4.96                                                                             7.43                                                                             -- 7.44                                                                             7.44                       __________________________________________________________________________

The results set forth in Tables 4-6 demonstrate the effectiveness of theclaimed anticoaguant in not unduly decreasing the ionized calciumconcentrations in sampled whole blood. It can be seen that the bestresults were obtained through the use of the most preferred composition,i.e. that produced with the use of 5 grams of zinc acetate per 15 gramsof initial heparin.

We claim:
 1. An apparatus for use in the collection of bloodcomprising:(1) a receptacle means defining a blood receiving spacetherein for receiving a blood sample; (2) a blood inlet means forintroducing a blood sample into the blood receiving space; and (3) ananticoagulant present within said blood receiving space, saidanticoagulant having been produced by a process comprising:a) contactingan aqueous solution of sodium heparin with an acidic ion exchange resinfor a period sufficient such that aqueous effluent produced possesses apH of about 3 or less; b) reacting said effluent with a heavymetal-containing compound suitable to produce a heavy metal heparinsalt; and c) reacting said heavy metal heparin salt with an aqueoussolution of lithium salts in sufficient amounts such that the resultingsolution exhibits a pH of about 6 to about
 7. 2. The apparatus of claim1 further comprising filtering the solution resulting from step (c). 3.The apparatus of claim 1 wherein the solution utilized in step (a) has aconcentration of about 30,000 to about 50,000 u/cc.
 4. The apparatus ofclaim 1 further comprising drying the solution resulting from step (c).5. The apparatus of claim 4 wherein the solution resulting from step (c)is dried by lyophilization.
 6. The apparatus of claim 1 wherein theacidic ion exchange resin comprises a resin with a sulfonic acidfunctionality.
 7. The apparatus of claim 6 wherein the acidic ionexchange resin is selected from the group consisting of IR-120 andIR-120 in the hydrogen form.
 8. The apparatus of claim 1 wherein theheavy metal-containing compound comprises a zinc, barium or copper saltand the lithium salt is lithium hydroxide.
 9. The apparatus of claim 8wherein the heavy metal-containing compound is selected from the groupconsisting of zinc acetate dihydrate, zinc chloride, zinc sulfate,barium acetate, barium chloride, barium sulfate, copper acetate, copperchloride, cooper sulfate and mixtures thereof.
 10. The apparatus ofclaim 1 selected from the group consisting of a capillary tube, syringeand vacuum container.
 11. The apparatus of claim 10 wherein theapparatus comprises a syringe.
 12. The apparatus of claim 1 wherein theheavy metal-containing compound comprises zinc acetate dihydrate. 13.The apparatus of claim 12 wherein zinc acetate dihydrate is utilized inamounts ranging from about 2 to about 7 grams per each 15 grams ofsodium heparin used in step (a).
 14. The apparatus of claim 13 whereinabout 5 grams of zinc acetate dihydrate is utilized per each 15 grams ofsodium heparin used in step (a).
 15. An apparatus for use in thecollection of blood comprising:(1) a receptacle means defining a bloodreceiving space therein for receiving a blood sample; (2) a blood inletmeans for introducing a blood sample into the blood receiving space; and(3) an anticoagulant present within said blood receiving space, saidanticoagulant having been produced by a process comprising:a) passing anaqueous solution of sodium heparin through a bed of an acidic ionexchange resin to produce an aqueous effluent having a pH of about 3 orless; b) reacting said aqueous effluent with zinc acetate dihydrate inamounts ranging from about 2 to about 7 grams per each 15 grams ofsodium heparin used in step (a); c) reacting the product of step (b)with an aqueous solution of lithium hydroxide sufficient to produce asolution having a pH of about 6 to about 6.5; d) optionally, filteringthe solution of step (c); e) optionally, drying the solution of eitherstep (c) or step (d).
 16. The apparatus of claim 15 wherein the solutionof step (a) has a concentration of about 30,000 to about 50,000 u/cc.17. The apparatus of claim 15 wherein zinc acetate dihydrate is utilizedin step (b) in an amount of about 5 grams per each 15 grams of sodiumheparin acid in step (a).
 18. The apparatus of claim 15 wherein thesolution of step (c) is filtered with a filter media having a pore sizeof about 0.22 microns.
 19. The apparatus of claim 15 wherein thesolution of step (c) or (d) is dried through lyophilization.